The finding may represent a significant gain against iron deficiency, which afflicts 30 percent of the world's population. It could refute belief that iron in the form of ferritin in soybeans has poor bioavailability and thus is not readily absorbed into the body once ingested.
In the study, 18 female volunteers — most of whom had marginal iron deficiency — showed iron absorption rates above those expected when they ate soybeans prepared as broth and muffins. They ate the muffins and had their iron measured 14 days later, then repeated the process with broth.
The absorption rate of iron in the study averaged 27 percent, exceeding the 5 to 10 percent expected, based on prior studies conducted with humans. It is believed that use of a soybean variety high in ferritin caused these elevated levels.
This work began in 1994 at North Carolina State University in Raleigh and at the ARS Soybean and Nitrogen Fixation Research Unit on the school's campus. The recent findings were made at Penn State University's General Clinical Research Center.
Ross Welch, a plant physiologist with ARS' Plant, Soil and Nutrition Laboratory in Ithaca, N.Y., assisted by growing soybeans with a radioactive isotope of iron that made it possible to "label" the iron in seed ferritin, making it detectable in red blood cells. Welch cautions that the results are not unequivocal because not all of the iron in the soybeans used was in the ferritin form. This is being addressed during the study's current phase.
ARS is the chief scientific research agency of the U.S. Department of Agriculture.